[FFmpeg-cvslog] fate: only check stddev for acodec-ra144

Michael Niedermayer michaelni at gmx.at
Fri Jun 1 18:26:13 CEST 2012


On Fri, Jun 01, 2012 at 05:59:04PM +0200, Reimar Döffinger wrote:
> On Fri, Jun 01, 2012 at 12:20:25PM +0200, Michael Niedermayer wrote:
> > ffmpeg | branch: master | Michael Niedermayer <michaelni at gmx.at> | Thu May 31 03:08:56 2012 +0200| [e6866b1c6702aee5b696c5a49c20edb136e0427c] | committer: Michael Niedermayer
> > 
> > fate: only check stddev for acodec-ra144
> > 
> > ra144 uses floats so bitexactness cannot be guranteed
> > This should fix a long standing issue with icc
> 
> Not to complain, but did you investigate?
> The fact that all other compilers, and even ARM, x86, x86_64 using SSE,
> PPC,... all give exactly the same result made me suspect that there
> is actually something at least strange but possibly wrong either
> with ICC or with the code.

the PSNR value stays the same with the printed precission
the stddev value changes by 0.004% the MAXDIFF stayed the same
and so did the length
and IIRC icc is able to do some advanced float optimizations which
are enabled by default
above feels like consistently pointing to a minor float optimization
difference.
Either way i think it would be a good idea to add 32 & 64bit ICC
instances to fate that use
-fp-model precise –fp-model source

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

it is not once nor twice but times without number that the same ideas make
their appearance in the world. -- Aristotle
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